Penetration and cratering experiments of graphite by 0.5-mm diameter steel spheres at various impact velocities
Introduction
One of the major concerns for spacecraft or high-power laser applications is the cratering process in brittle materials under high- and hyper-velocity impacts (HVI). Among them, carbon is of particular interest because it is a common elementary component in composite materials. Indeed, they are widely used in aerospace industry owing to their low density and high mechanical properties. In that specific case, meteoroids may impact satellites at several kilometers per second, possibly damaging or destroying some vital equipment [1], [2], such as tanks. Moreover, the ejection of secondary debris created by previous impacts can remain on orbital trajectories and hit other man-made space structures [3]. Similarly, the various instruments used in the Laser MégaJoule (LMJ) experiment chamber may be struck by a variety of shrapnel and debris originating from the target assembly after intense laser shots [4], [5].
The range of materials exposed to HVI is significant. Metals have been widely studied, both experimentally [6], [7], [8], [9] and through the use of numerical hydrocodes [10]. Brittle materials have also been included in previous studies, such as geophysical materials [11], silica glass [12], [13] or building materials [14], [15], [16]. For the latter, the depth of penetration (DOP) is particularly analyzed as a performance criterion. Concerning composites, studies have already been conducted [17], [18], but it appears there is a lack of knowledge about damaging and cratering processes of elementary components such as graphite matrix or fibers. Experimental results have been published giving crater dimensions in porous graphite for a variety of projectile materials and velocities [19], [20]. The present authors have attempted to compute numerical models into hydrocodes to reproduce experimental results [21]. However, a large set of experimental data was missing in order to fit the parameters of the models, especially that of the projectile such as elastic limit and strength which may be highly dependent of the strain rate [22].
In this paper, we present experiments leading to crater formation and penetration of a steel projectile into a commercial grade of polycrystalline graphite. In the following section, we describe the dynamic experiments on thick targets and display new results. Then, Section 3 will be devoted to the discussion of the data obtained by post-mortem tomographies on the recovered samples. Finally, in Section 4, we will try to get a better insight into the penetration processes.
Section snippets
Experimental
We recently conducted cratering experiments with 0.5-mm diameter AISI 52100 steel spherical projectiles and 30-mm diameter, 15-mm long graphite targets. This graphite is a commercial grade from the POCO company [23] and is macroscopically isotropic with a density of 1754 kg m−3. Its main mechanical characteristics have been published in Ref. [24] and are recalled in Table 1 along with those of hardened AISI 52100 steel. Indeed, projectiles stem from bearings involving a high Rockwell hardness
Crater depth and diameter
The crater diameters and depths normalized by the projectile diameter are plotted in Fig. 1. As expected, they strictly increase with the impact velocity, apparently following a power law. Previous studies about spherical projectiles impacting various ductile materials used a 2/3 power law which is linked to the hemispherical shape of the resulting craters [6], [7]. However, in the study of steel spheres impacting graphite brittle targets, Tanabe et al. [19] have noticed the same law with
Penetration without fragmentation (R1 and R2)
Here, we try to explain by two methods the successive increasing and decreasing of the projectile depth of penetration below 3.2 km s−1.
Take for example two shots with similar DOP yet different velocities, #68_13 (R1) and #72_13 (R2). It implies that the kinetic energy of the second is about 1 J greater than the first one. Consequently, the projectile of the second should be the deepest but that is not the case. Considering that #72_13 belongs to the regime where the projectile suffers plastic
Conclusion
We displayed new cratering and penetration experiments with 0.5-mm diameter steel spherical projectiles and thick cylindrical graphite targets at velocities between 1.1 and 4.5 km s−1. Post-mortem tomographies revealed that the projectiles were trapped into the target after the re-closing of the graphite. The characteristic dimensions of the craters such as volume, diameter and depth were measured and all of them increased with the impact velocity. But contrary to ductile materials, diameter
Acknowledgments
The authors express their gratitude to Stéphanie Tastet for performing the experiments and to Patrick Brelivet for the tomographies. They would also like to thank Claude Bianchi who accepted to revise the English of this paper.
References (29)
A career in applied physics: Apollo through space station
Int J Impact Eng
(1999)- et al.
Computer models of micrometeoroid impact on fused silica glass mirrors
Int J Impact Eng
(2003) - et al.
Hypervelocity impacts on thin brittle targets: experimental data and SPH simulations
Int J Impact Eng
(2006) - et al.
Using silica aerogel to characterize hypervelocity shrapnel produced in high power laser experiments
Int J Impact Eng
(2003) - et al.
Experimental laws of cratering for hypervelocity impacts of spherical projectiles into thick target
Int J Impact Eng
(1994) - et al.
Penetration of 6061-t6511 aluminum targets by ogive-nose steel projectiles with striking velocities between 0.5 and 3.0 km/s
Int J Impact Eng
(1999) - et al.
Penetration experiments with 6061-t6511 aluminum targets and spherical-nose steel projectiles at striking velocities between 0.5 and 3.0 km/s
Int J Impact Eng
(2000) - et al.
Hypervelocity impact testing of transparent spacecraft materials
Int J Impact Eng
(2003) - et al.
Application of a computational glass model to compute propagation of failure from ballistic impact of borosilicate glass targets
Int J Impact Eng
(2013) Modeling experiments of hypervelocity penetration of adobe by spheres and rods
Procedia Eng
(2013)
Penetration of grout and concrete targets with ogive-nose steel projectiles
Int J Impact Eng
{HVI} tests on {CFRP} laminates at low temperature
Int J Impact Eng
Hypervelocity impact damage to composites
Compos Part A: Appl Sci Manuf
Crater formation of carbon materials by impact of a high velocity sphere
Carbon
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